Process of producing colored images.



UNITED STATES PATENT OFFICE.

EDMUND R. BULLOCK, OF ROCHESTER. NEW YORK, ASSIGNOB TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OI NEW YORK.

PROCESS OF PRODUCING COIbRE-D IMAGES.

No Drawing.

To all whom it may concern:

Be it known that I, EDMUND R. BULmcK, residing in Rochester, county of Monroe, State of New York. have invented new and useful Improvements in Processesof Producing (.olorcd Images, of which the following is a specification.

This invention relates to photography and more particularly it relates to the production of colored images. In my process I obtain, preferably from a primary photographic image of the silver species, an intermediate image containing chemically active substances and treat it with suitable compounds which, upon reacting with said image. produce insoluble colored substances or dyes, the result being a colored image having the same general size and gradations as the primary'image. Such image may then be fixed.

One object of my invention is to provide a process of this kind which will easily yield images of clear, brilliant, durable, readily re1') rodueible.' and definite colors on apcr, glass, film. or other base. Another ob ect of my invention is to form an intermediate image of. metallic insoluble salts of such a nature and of such a state of high oxidation that they will have strong oxidizing tendencies toward the organic compounds with which they react to form the colored image; yet will themselves be not reduced to the metalbut merely to a salt. which is in a low state of oxidation and is easily removable by a fixing bath. In other words I aim to carry on the color forming reaction on what may be termed a relatively high plaue of oxidation, none of the reaction products bein reduced to the-lowest limit, the words oxidation and reduction being used herein with the broadest chemical significanoe to refer to chemical bonds and clianges't herein generally, and not merely to oxygen content. A. third object of my'invention is to provide a bleaching bath or -stepwhich will act rapidly to produce this intermediate or secondary ima ge. yet will not cause injury to such image or its support, if the bath be used for a rolonged time. A

fourth object is to provide a process which may he carried out by using relatively inexpensive baths of good keeping quallties. A

Specification of Letters Patent.

Application filed March 7, 1917.

fifth object of my invention is to employ in the fixing 7 operation a bath which will quickly dissolve metallic salts but will not appreciably reduce or injure the insoluble colored image. A sixth object of my invention is to provide auxiliary clearing and washiu" steps where necessary. Other objects will hereinafter appear.

To enable those skilled in the art to use my invention. I shall now describe certain specific embodiments thereof but it is understood that these particular embodiments are merely illustrative and the scope of the invention is not limited to these described examples except as indicated in the claims.

As one example of my process I will explain its application to the production of colored images on paper starting with the usual image composed of minute silver particles suspended in "any ordinary colloid. such as gelatin or eollodion. The silver image is iunnersed in a bleaching hath made up of 4 parts of a 10)? potassium ferricyanid solution and 1 part of a 1% potassium permanganate solution. The image is changed to a uniform yellow or orange color and the bath can be used repeatedly. but in the caseof an old bath it is often advisable to filter it and then add about one-tenth of its volume of potassium permanganate solution. This is to keep the bath iua sufiiciently oxidizing condition to prevent the formation of silver ferrocyanid, which salt is useless at this stage of the process, the yellow silver ferricyanid with its high state of oxidation being the salt desired.

VVhen the bleaehin is complete. the image or print removed mm the bleaching bath and washed in running water. The first washing may vary according to the support for the image and usually will not exceed thirty minutes. i

The !print containing the intermediate image of practically insoluble silver ferricyanid at this state of the process will often show brownish stains. probably due to manganous ferricyanid. These may be removed by immersion for 5 to 10 mimites in a hath containing 3 of oxalic acid rrystala. The print should he left in the clearing hath some time after the disappearance of the brownish stains to entirely remove the m1- desirahle salts. Should white manganous ferrtwyauid separate from a used oxalic acid hath it should he removed liefore the hath i again used or a fresh hath lltllll(l l)t prepared. After the clearing operation. the print i 1 again washed. say 20 mmutes. H1. running' water and the seeomlary Image ot silver ferrieyanid will then he complete and may he either dried and kept for a suhsequent toning or transferred at once to the toning bath.

Alternatively the silver fei'lic \al1id image nlav he formed l1 bleaching the ilver image in a hath composed of .3 ])2ll'l ot' a 10'; potaaeium ferricyauid solution and i parkof a H); chromie auhydrid tt'rtl olut1on. This hath :lt'ts fairly qui kly. '3 minutes heing a common time for lileaehing. clear i115! hath is not needed after it but a lone washing is sometimes necessary and may last for two hours in running water. In use this alternative hath may require a little practice in manipulation.

'hichever bleaching hath i. ltsttl, 1t .\hould he free fr m more than traces of chloride. The wash water should also he. rea. onahl\' free from them heeause the. ehlorids iuight change some of the silver t'erricvanid to s'lver elilorid thu weakening the oxidizing power of the intermediate image.

The toniu; bath in which the ferriovanid image i. next'iiumersetl in a solution containing organic Hllbltllltt'fi which are capalile ol' lvcing oxidized by the action of silver ferricvanid into in olulile colored substances. examples of such uhstances I may name (ll heuzidin which gives a strong blue image: (:2) (l-tolidiu which giveaa strong reeu image: (2 3) paramidophenol together with alpha-naphthol which give a red nnage; (4) 1iara ihenylenediamin which gives a purpliah image: (5) alpha-11a ihthyla n n which gives a reddish-purplez -(ti) (lltHllF-ltlln hydrlahlorid which gives a strong green image. These illustratiom will serve to show the kind of materials which can he used in my process. The strength of the toning bath is not 0apeeially important. even fairlv dilute haths giving a rapld action which is often cou'aplete at the end of a minute.

The theory (which of course, not indispensable to practi ing my p'rm'ess) is that these organic rulnpulllitla act 11 reducers which change the silver ferricyanid of the seeondarv image into silver ferrocyauid and are theinhelves oxidized to colored substances whieh are insoluhle and are formed or deposited in such a way as to create. a colored image having the same general form. size, and ,Ililtlilllflll as the original or primary ilver image. liy thus keeping the reaction on a high plane of oxidation I am able to take advantage of the greater chemical activity in the formation of colored anhstancea possessed by highly oxidized Ralts, such as terricyanidswhile obtaining at the 0nd of the reaction a altot'lmveroxidatiou which is more. easily removed without injury to the colored inrage. than would he the ease if the reaction had been on a lower level of oxidation and a metallic precipitate. like. silver, had been produced.

The toned print is washed. say for five minutes. in running water to remove the 0.\'- eess of the toning hath. For some purposm the compound image of silver ferrocyanid and insoluble coloring matter may he sati factory and sutlieient.

It is often desirable. however, to eliminate the silver salts without injuring or disturhing; the coloring matter, thus enhancing the transparency of the colored image. Due to the fact that the toning reaction has been on a relatively high plane of oxidation, thus resulting in silver ferrocyanid instead of metallic silver, this removal of the silver salt can be easily effected. If the original bleaching bath was the one containing potassium permanganate, the colored image is treated a short time, say 1 minute, in a bath containing sodium thiosulfate. crystals 35 part potaasiuin chromate 1 part, and water to 100 parts. The proportions of this bath a re. of course, variable. but I have found the ones given to be very eflicient. Such a bath i7 mildly alkaline and so stable that. it can he hoiled. The chromate checks any tend ency to reduce the colored image. However, where the. original bleaching bath contained the ehroniie anhydrid, this tendency toward reduction in the fixing bath does not prevail and a plain sodium thiosulfate fixing bath may be employed.

The fixed image or print is now waaned for a time, sufficient to remove soluble crystalline salts therefrom.

In another species of my invention I may ohtain an image of silver fcrricyanid as hereinabove explained and then treat: the Fillllt with a solution of manganous bromid, whereby a mixed image of silver bromid and manganoua ferricyanid is formed. This image (after washing) is treated or toned with organic substances, such as benzidin and henzidin derivatives, to give colored images, the organic reducer being oxidized to n-oduce an insoluble colored substance. and the manganous ferric vanid being reduced to manganous ferrocyanid. If desired. the ailver bromid may be dissolved out before the toning bath is used by bathing in a 3!? solution of potassium cyanid, such ricvanid-and-l-part of 1? manganate.

operation leaving the manganous ferriovanid uniin 'mi'rcd. Experiments with silver hromid alone liow that such substance does not react on'the henzidin. etc. to produce a color and. consequently. the active rc-agent in the. mixed iii-age is, the manganous ferricyanid.

I claim:

1. The process of producing colored images which comprises forming-an image cmllpnsed of metallic salt in a high state of oxidation and reducing said salt to a metallic' salt of" a lower State of oxidatitlni by treating said image with an organic reducing compound which is simultaneously oxidized to produce an insoluble colored compound forming'a colored image.

2. The pl'tk't'fifi of producing a colored image which comprises forming an image of an insoluhle-l'crricvau=id. and reducingit-to the. corresponding ferrocyanid lrv treating it with an organic compound which simultaneoust) oxidized to produce an insoluble colored sllhstancc forming a colored image.

3. The prm-css of prmlucing colored images which comprises forming an image of silver t'erriqvanid and reducing itto Silver fcrrocvanid by treating said'image with an organic compound which is simultaneously oxidized to. prodnce an insoluble colored compound forming a colored image.

.lf 'l he in o co s of producing a colored im- ,agc from a primary image which comprises mam-mug aaid silver image'into uninter- -lmaliatrdmage o f'sllver f('I'l'l(3 \'ilIll(l and re id 1 silver ferrie vanid to silver ferduring uhstance forming a colored 1. F15: j

"i. "i" 'lzw it. In the iroeess of producing a colored imag a ll'roini coon 'trtat ng said image in a bath of potassium. flerricyanid and potaaaiumf per- IIFiJ L'H treatingithe silver image in a bath xrtassium fercontaining4'=parts of 10C? [)OltlSSlUlll per- 8. The process of producing a colored imlit treating said silver 'ferrieyanid p I i ttrgiinic reducing compound wh ch" inlrtltairehttaly oxidized to produeean l ll- Qa lvcr image the step which colored insoluble substance intact.

9. The Pl'UttSs of prmlucing a colored image from a silver imag wlin-h comprises, converting said-sliver image into an Intermediate imag* of silver ferricyanid, reducing said intermediate image to silver ferrocyanid h treating it with an organic reducing compound which is sinnlltaneonsly oxidized to produce an insoluble substance forming a colored image. and finally fixing said colored image in a mildly alkaline bath containing a solvent of silver ferrocyanid together with a mnall percentage of an oxidizing agent.

10. In the process of producing a colored image. the step of treating an image con taininga silver salt and insoluhle colored substance in a bath containing sodium thinaulfate and a relatively small amount of potassium chromato- -11. In the prmess of producing a colored image, the step of treating an image con taining a silver salt and an insolublecolored enlistance in an aqueous hath containing 35?? of sodium thiosnlfate crystals and 1% potassium ehromate.

1:2.' The process of producing a colored image from a silver image which comprises converting said silver image into a intermediate image of silver ferrieyanid. washing the latter. treating the intermediate im' age in a clearing hath. again washing said intermediate image. and reducing sa id inter mediate image by treating the same with an organic reducing emnpound which. is. aimnltaneouslv oxidized to produce an. insoluble colored substance forming a colored image.

In the process of prodncing eolored images. the steps of convertingasilver image into-a silver ferricvanidimage in; treatment ina hath containing potassium ferricyanid and potassium permanganatei.washing the secondarv image thus obtained-treating said secondarv image in a hath ofroxalie acid until the image is cleared fronrsta in. and washing said image to prtnlnceayellowish image of silver ferrievanid free mm stain and soluble salts.

1i. The process of prodl lcing a colored image from aailver image which comprises converting xaid silver image into an intermediate image of silver ferrieyamd liytreatment in a hath containing potassium ferricyanid and potassium permanganate, Washing. treating said intermediate image in a clearing hath (:mli uining uxnlic :u'id, washing sanl intvrnn-dmtv nnngrmu'ruihu-ing said 5((f0lHhll'y image h treating i1 with :in or- ;mmc rmhn'mg min mum] which 15 simulwashing, civaring in hnih ()f oxalic acid,

Washing. reducing in n hath nl' honzidin 15 h 'i h'ovhlmnL washing, fixing in the bath i-nntnining smlilun thiosnltuiv and u snnill quantity of an oxidizing agent, and finally USilil'lg.

In twstimony whvrmi". I have signed this 20 spm'ifix'ntiun in thv pl'usi'ncu of (Wu witnesses lhis 2nd till) of March, [017.

I). R. HILLOCK. \Vitnessos:

I. A. SCH. 1'1'1, R. I). S'l'lNUIHHiLD. 

